1. Field of the Invention
This invention relates to a dental x-ray assembly, and more particularly, to an adjustable linkage mounting assembly for articulating arms of a dental x-ray assembly.
2. Description of the Prior Art
In dental operatories, a dental x-ray system is generally cantileverly positioned by a vertically-disposed shaft member in a mounting frame or bracket mounted to a vertical support member, such as a wall. The dental x-ray assembly includes a horizontally-disposed extension arm member mounted to the vertically-disposed shaft member disposed for rotation in the mounting assembly. At an end of the horizontal-disposed extension arm member remote from the mounting member, there is included vertically-disposed inner and outer positioning arm members articularly mounted therebetween to each other. To the outer arm member, th ere is provided an x-ray tube head assembly extending downwardly from an end of the outer arm member for appropriately positioning an x-ray generating member of the x-ray tube head assembly at a point proximate a patient's oral cavity to effect imaging of such preselect portion thereof.
The articulating arms have been provided with springs to counter balance the weight of the tube head. However, the spring force and mechanical advantage of the spring force relative to the weight of the tube head vary continuously throughout the motion of the articulating arms. It is therefore difficult to compensate for the weight of the tube head for all of the positions of bar linkages necessary in order to obtain all of the necessary x-rays of the patient's oral cavity. The x-ray tube head has a tendency to rise or fall in certain positions which is detrimental to the operation for obtaining accurate x-ray information.
One solution to the problem was an attempt to dampen the system through the use of a friction washer positioned between the articulating arms on the far linkages thereto with a threaded fastener. However such solution suffered from the disadvantage that it is sensitive to adjustments and friction forces change rapidly with wear.